1. Field of the Invention
The present invention relates to filter elements and, more particularly, to standard and coreless filter elements having pleated filters with a foam girdle to secure the pleats.
2. Brief Description of the Prior Art
Fluid systems often include an in-line filtration system for filtering out particles or other impurities in the fluid. The in-line filtration systems generally include a housing forming a hollow center chamber, a fluid inlet port, and a fluid outlet port. A replaceable filter element, usually forming a plurality of pleats, is positioned inside the hollow center chamber of the housing. An example of such a pleated element is disclosed in U.S. Pat. No. 3,552,553 to Redding. The fluid enters the inlet port of the filter, which is generally positioned at an outer edge of the housing, flows through the replaceable filter element, and exits the outlet port which is usually positioned adjacent a center portion of the housing.
One drawback of liquid or fluid filters having pleated filtering elements is that the spacing of each individual pleat can vary as the differential pressure of the fluid passing through the pleats is increased. Upon filtration of high viscosity oil, for example at cold start-up, the pleats may move toward one another causing bunching which restricts the flow of fluid flowing through the filter and also decreases the effectiveness of the filter. Pleat stability is not a significant concern in air filtrations systems such as disclosed in U.S. Pat. No. 5,858,044 to Nepsund.
One approach to overcoming this problem is disclosed in PCT application WO 97/31695. That application discloses using a spun-bonded support disposed within a cylindrical, internal cavity formed by a pleated filter element. Internal peaks of the filter element, formed by the pleats, are glued to the support wrap to increase the stability of the filter element and maintain separation of the pleats. One drawback of that approach is the manufacturing and material costs associated with accurately fixing the internal peaks of the pleats to the support wrap such that the pleats are evenly spaced.